This invention relates in general to a method and apparatus for controlling a fluid for a discrete/pulse dispensing application.
The present invention relates to an interior panel for a vehicle, and in particular to a headliner. A headliner typically consists of various layers or plies, such as a stiffening and silencing layer. Such layers can be formed, at least, of a rigid carrier layer which is integrated into the vehicle interior panel. Moreover, the interior panel typically further consists of at least one decorative layer and an intermediate shock-absorbing layer. Such an interior panel with an integrated stiffening and silencing layer may, in particular, be designed as an acoustic headliner when used as a roof liner. The interior panel is typically prefabricated and is mounted at a corresponding place of the vehicle, such as the interior of the vehicle roof. However, such a special construction of the roof liner is not needed according to the invention.
The process of forming a vehicle or automotive headliner typically includes cutting a thin sheet of polyurethane foam and coating the foam with a reactive component in a liquid state which polymerizes to form a polyurethane which stiffens the substrate. Multiple layers (or plies) may be so coated and pressed together to provide a desired stiffness. Another method includes a liquid or multiple reactive components in liquid form being sprayed onto a sheet of material as it passes on a conveyor. Still another method is roll coating, wherein sheet material is fed between rolls which are coated with a liquid which transfers the coating onto the workpiece. Roll coating is not necessarily a separate method, but can be used in conjunction with a spraying apparatus. For example, roll coating applies one of the chemical agents and spraying applies a second agent.
In the manufacture of automotive headliners using a spray coating method, there has been a need to control the “catalyst” that is applied to the manufacturing process. The term “catalyst” is generically used to describe the polyurethane catalyst that is used in conjunction with polyurethane adhesives to collectively form a bond between the various plies of an automotive headliner. Controlling the amount and spray pattern of catalyst has been a difficult task. Typically, the catalyst application process requires very low pressures for very short time intervals. For example, a catalyst could be dispensed at about 5 p.s.i. for a relatively short period of time (on the order of seconds), and then the apparatus would be turned off for a relatively longer period of time (on the order of about one minute). It would be typical for an on/off cycle to comprise a total of one minute, with the “ON” time equaling a few seconds and the “OFF” time equaling the remaining time.
Historically, the dispensing pressure of a fluid in a dispensing apparatus has been controlled by a mechanical (spring and diaphragm) pressure regulator. Such regulators have shortcomings when used for controlling pulse fluid applications. For example, regulators “creep”, which means that during periods of inactivity (such as the exemplary relatively long “OFF” time) there is a tendency for the regulator to pass fluid and build downstream pressure. This is because regulators are best equipped to operate in a continuous flow situation. Regulators can also be unreliable at the low operating pressures required for intermittent spraying operations because regulators have an inherent quality of operating with a fluctuating pressure. Thus, an apparatus that is more precise at low pressure would be advantageous for the application of a catalyst. Regulators can also have a slow response time to an actuation signal. Additionally, when flow amount is based only on pressure and flow opening, the actual amount of material dispensed is not measured. Thus, a more accurate apparatus for determining and controlling an amount of catalyst/fluid dispensed would be beneficial. Regulators also eventually wear out after prolonged use. Finally, traditional regulators offer no vent for bubbles or gases entrained in the fluid to escape.
Therefore, for in order to limit the shortcomings of using regulators in a catalyst dispensing system, and to obtain the advantages described above, it would be beneficial to implement a novel method and apparatus for dispensing a catalyst/fluid.